Of the worlds proven oil reserves, over half are considered heavy oil and many of these are new production areas with rapidly evolving technology and new demands. One of the most challenging aspects of such heavy oil production is the transport of these highly viscous fluids. Transport of viscous fluids along pipelines for crude oil production, delivery to a refinery, or other storage facility presents a myriad of challenges. One major challenge is recovering and transporting high viscosity petroleum products from well sites to refineries or storage facilities. In many proven petroleum-containing sites, very little petroleum may be obtained by known means because of the high viscosity of the petroleum products.
When extracted from the subterranean formation, the viscous oil must be transported from the field to a refinery or shipping terminal. Various techniques are known for aiding in the recovery of viscous petroleum and facilitating its transport to a refinery, storage site, or other location. These techniques include, for example, mechanical pumping, mechanical pumping combined with steam injection, and mining. Pumping unit limitations have a negative impact on the economics of producing viscous oil from pumped wells found in many parts of the world. The high viscosity of these crude oils results in low pump volumetric efficiency, reduced flow rates, and high flow pressure drop.
Heavy oils exhibit a viscosity generally from 10,000 to 500,000 cP at room temperature. As a result, according to current practice pumping and heating stations are used to maintain a low viscosity for transport along pipelines. However, prolonged pumping interruptions often occur resulting in cold crude oil with concomitant plugging of pipes and pumps. Insulating hundred of miles of pipe to reduce heat loss is usually cost prohibitive. Heating the crude oil likewise consumes a large amount of energy and is cost ineffective. Diluents (e.g., fuel oil or kerosene) are sometimes used to reduce viscosity for pumping and transport. However, the large amount of diluent required is not readily available in the production area and, furthermore, in existing practices, the diluent has to be recovered at the fluid delivery site and pumped back to the field over great distances.
Current production of heavy oils (defined herein as having an API gravity of 20 or less) from the subterranean formation to the processing facilities results in significant pressure drop, fatigue of pumping equipment, and low fluid flow production rates due to the high viscosity of the crude oil component of the production fluid.
There thus exists an ongoing need for improved methods to decrease the apparent viscosity of produced fluids to improve pump performance and operating efficiency thereby enhancing production. There exists a specific need for enhancing recovery and transport of viscous and extremely viscous petroleum such as that found in heavy oil reservoirs and other deposits.